The present invention relates generally to methods for producing gene products. More particularly, it relates to a method for enhanced production and recovery of phosphate starvation inducible gene products.
By way of further background, bacteria use phosphate, phosphate esters, or phosphonates as phosphorus sources for growth. However, phosphate is the preferred phosphorus source. When in excess, phosphate leads to repression of genes for use of alternative phosphorus sources, phosphate esters or phosphonates. Genes for use of alternative phosphorus sources are turned on several hundred fold during phosphate limitation. Such genes are phosphate starvation inducible and are thus known as PSI genes. As to utilization of phosphonates, it is known that two pathways for their breakdown exist. These include the carbon-phosphorus ("C-P") lyase pathway and the phosphonatase pathway. As is known, these pathways are distinguishable by substrate specificity and product formation.
Phosphate limitation, which by nature limits growth yield, is a conventional means for the expression of both natural and synthetic PSI genes at a high rate to provide gene products used in assays (e.g. immunoassays), therapies (e.g. growth hormones) and other applications. However, phosphate starvation limits growth yield, and thus the final (total) amount of the PSI gene product is limited, as well.
In light of this background there continues a need for an economical method for enhancing the production and recovery of PSI gene products which does not suffer from limited growth yield. The present invention addresses this need.